Lubricant supply safety system

ABSTRACT

A lubricant supply safety system for a machine comprises a reservoir for lubricating oil, a hydraulic motor driving one or more feeder pumps supplying lubricating oil from the reservoir to various points in the machine, a first pump for supply of lubricating oil from the reservoir to drive the hydraulic motor under normal operating conditions, and a second pump driven by the machine for supply of lubricating oil from the reservoir to drive the hydraulic motor in the event of failure of the first pump.

BACKGROUND OF THE INVENTION

The present invention relates to a lubricant supply safety system for amachine, comprising a reservoir for lubricating oil, a hydraulic motordriving one or more feeder pumps supplying lubricating oil from saidreservoir to various points in said machine, a first pump for supply oflubricating oil from said reservoir to drive said hydraulic motor undernormal operating conditions, and a second pump for supply of lubricatingoil from said reservoir to drive the hydraulic motor in the event of afailure of said first pump.

Even a very temporary absence of lubricating oil to an expensive pieceof machinery can have devastating and expensive consequences. Severalmethods have therefore been developed to assure that lubricant willcontinue to be pumped to the machine even in the event of a pumpbreakdown or a power failure. This is particularly important in machineswhich require a long time period to stop due to a heavy moving mass orif they must be emptied of material being processed before they can bestopped. Two or more pumps, for example, can be arranged in parallel sothat if one pump should fail, the other pump or pumps will continue toat least supply partial oil pressure to the machine. There is adisadvantage, however, that in a system with only two main pumps, theflow delivered in this failure situation will only be 50% of the normaloperating pressure. Parallel backup systems have also been used whichrequire mechanisms for the backup pump to kick in in the event of afailure of the normal pump. Such backup systems require that the backuppump be started immediately in the event of a failure of the first pumpand that they have a power source, usually an electric motor which isintact and is supplied with electric current. In the event of anelectrical power failure, a backup pump powered by an electric motor maybe rendered useless. Also, one can never be 100% sure that a backuppump, which only kicks in in the event of a failure of the normal pump,will start running immediately and is in proper functioning order.Frequent tests are required in this case to maintain such backupreliability.

SUMMARY OF THE INVENTION

These disadvantages of the prior art are removed in a lubricant safetysystem as described by way of introduction which is characterized inthat said second pump is continuously driven by said machine and isautomatically engaged by means of a valve device to drive said hydraulicpump immediately upon detection of a malfunction of said first pump. Alarge piece of machinery with a large rotating mass, for example, orwhich must be emptied before it can be stopped may require a run-downtime of 20 minutes more, and if the second pump is continuously drivenvia a belt whenever the machine is in motion, it will already be inoperation when it is needed to supply high pressure oil to the hydraulicmotor. Since said second pump is driven continuously, it will in a sensebe continuously tested and any malfunctioning thereof can be immediatelydetected.

According to a preferred embodiment of the lubricant supply safetysystem according to the invention, the continuously driven second pumpis connected via the valve device under normal operating conditions to alow-pressure line returning oil to said reservoir. Since the second pumpis under normal operating conditions never loaded to supply highpressure, it will not be subjected to high-pressure stresses and cantherefore be operated for very long time periods without any foreseeableproblems.

Further advantages can be obtained by including in the low-pressure linean oil filter and an oil cooler. The second pump is therefore made useof during normal operation for the functions of filtering and coolingthe oil. According to a further advantageous embodiment of the lubricantsupply safety system according to the invention, added reliability isobtained by mechanically biasing the valve to move immediately to thefail-safe position when the first pump fails to deliver pressurized oil.This allows the safety system to be independent of any electricalcurrent or electrical circuitry whatsoever.

According to another further embodiment of the invention, thelubricating oil reserve is divided into first and second compartments bymeans of an overflow barrier. The first and second pumps draw oil fromthe lower second compartment and the feeder pumps draw oil from theupper first compartment. Said low-pressure line leads to the upper firstcompartment. Thus, the purified and cooled lubricating oil, which isused to lubricate the machine, will not be mixed with the oil used torun the hydraulic motor.

The invention will be described below in more detail with reference tothe accompanying drawing, which shows schematically the construction ofa lubricant supply safety system according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of the lubricant supply safety system ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawing, the numeral 1 designates a first pump driven by anelectric motor 3, and the numeral 2 designates a pump connected by abelt or other connector 4 to a rotating component 5 of the machine 17 tobe lubricated. The pumps 1 and 2, respectively, each communicate on thesuction side via pipes 1a and 2a, respectively, with the warm oilsection 66 of a lubricating oil reservoir, generally designated 6.

The pumps 1,2 are connected on the pressure side via lines 1b and 2b toa flow valve 7. Said valve has two positions, the first of which (thecross over represented in the upper half of the valve 7) is assumed whenboth pumps are in normal operation. Lubricating oil from the first pump1 pressurizes the hydraulic motor 8 via a line 7a, and is returned viathe lines 8a and 7b to the upper compartment of the oil reservoir 6. Oilis pumped from the reservoir by the pump 2 through the line 2b and thereturn line 7b in the normal operating position of the valve. Thisposition is not shown in the drawing. This normal operating position canbe symbolically visualized as the valve 7 being moved downwards by thepressure delivered by the pump 1. There is a low-pressure filter 9 and alow-pressure cooler 10 in the return line for filtering and cooling thereturn oil.

Should the first pump 1 normally driving the hydraulic motor 8 for somereason not deliver pressure to the line 1b, then the valve 7 willautomatically assume the fail-safe position shown in the drawing. Thismay typically occur due to an electrical power failure, for example, butmay occur due to other malfunctions of the pump. A piece of heavyrotating machinery may take quite some time to be brought to astandstill, and during this time it is crucial that it still be providedwith lubricating oil. In the fail-safe position shown, the second pumpnow drives the hydraulic motor 8 at high pressure, thus assuring thatthe pumps 11-14 will supply the machine 17 with lubricating oil. Sincethe motor 2 normally runs at low pressure, it will have a long life andwill be running at the very instant when it is needed to drive thehydraulic motor 8. There is thus no delay or uncertainty as to itsoperation.

The hydraulic motor 8 is operatively connected to a number of feederpumps for supplying lubricating oil to the lubrication points of themachine 17. In the embodiment shown in the drawing there are four feederpumps 11, 12, 13 and 14 which communicate on their suction sides vialines 11a, 12a, 13a, 14a with the upper compartment 6a of thelubricating oil reservoir 6 and communicate on the pressure side vialines 11b-14b with the lubrication points 11c, 12c, 13c, 14c of themachine 17. As was mentioned above the lubricating oil reservoir 6 isdivided into two compartments 6a,6b. To the compartment 6b there issupplied via a line 15 new lubricant and from this compartmentlubricating oil is drawn via the lines 1a,2a to the pumps 1 and 2. Theline 7b supplies to the compartment 6a cold filtered lubricant. Fromthere the filtered and cooled lubricant is pumped via the lines 11a-14a,the feeder pumps 11-14 and the lines 11b-14b to the lubrication pointsof the machine. Surplus lubricating oil in the compartment 6a overflowsthe barrier 16 into the compartment 6b.

It will be obvious to the person skilled in the art that the inventioncan be varied in a number of manners within the scope of the invention.For example, the number of feeder pumps and the number of hydraulicpumps are of course not limited to the numbers shown in the drawing.

I claim:
 1. A lubricant supply safety system for a machine, comprising areservoir (6) for lubricating oil, a hydraulic motor (8) driving one ormore feeder pumps (11, 12, 13, 14) supplying lubricating oil from saidreservoir to various points in said machine, a first pump (1) for supplyof lubricating oil from said reservoir to drive said hydraulic motor (8)under normal operating conditions, a second pump (2) for supply oflubricating oil from said reservoir (6) to drive said hydraulic motor(8) in the event of a failure of said first pump (1), said second pump(2) being continuously driven by said machine and being automaticallyengaged by means of a valve device (7) to drive said hydraulic motor (8)immediately upon detection of a malfunction of said first pump (1). 2.The lubricant supply safety system according to claim 1, wherein saidcontinuously driven second pump (2) is connected via said valve device(7) under normal operating conditions to a low-pressure line (7b)returning oil to said reservoir (6).
 3. The lubricant supply safetysystem according to claim 2, wherein said low-pressure line (7b)includes a low-pressure oil filter (9).
 4. The lubricant supply safetysystem according to claim 2, wherein said low-pressure line (7b)includes a low-pressure oil cooler (10).
 5. The lubricant supply safetysystem according to claim 1 wherein said valve device (7) is biased to afail-safe position connecting said second pump (2) to said hydraulicmotor (8) when said detection of a malfunction is detection of anabsence of pressure in the oil delivered by said first pump(1).
 6. Thelubricant supply safety system according to claim 1 wherein said secondpump (2) is driven directly mechanically by said machine by means of abelt.
 7. The lubricant supply safety system according to claim 2 whereinthe lubricating oil reservoir is divided into a first (6a) and a second(6b) compartment by means of an overflow barrier (16), over whichoverflowing oil flows from the first (6a) to the second (6b)compartment, said first and second pumps (1, 2) drawing oil from saidsecond compartment, said feeder pumps (11, 12, 13, 14) drawing oil fromsaid first compartment (6a) and said low-pressure line (7b) leading tosaid first compartment (6a).
 8. A lubricant supply safety system for amachine, comprising a reservoir (6) for lubricating oil, a hydraulicmotor (8) driving one or more feeder pumps (11, 12, 13, 14) supplyinglubricating oil from said reservoir to various points in said machine, afirst pump (1) for supply of lubricating oil from said reservoir todrive said hydraulic motor (8) under normal operating conditions, asecond pump (2) for supply of lubricating oil from said reservoir (6) todrive said hydraulic motor (8) in the event of a failure of said firstpump (1), said second pump (2) being continuously driven by said machineand being automatically engaged by means of a valve device (7) to drivesaid hydraulic motor (8) immediately upon detection of a malfunction ofsaid first pump (1), and wherein the lubricating oil reservoir isdivided into a first (6a) and a second (6b) compartment by means of anoverflow barrier (16), over which overflowing oil flows from the first(6a) to the second (6b) compartment, said first and second pumps (1, 2)drawing oil from said second compartment, said feeder pumps (11, 12, 13,14) drawing oil from said first compartment (6a).